DTC P0742 TCC System Stuck On Buick Built Before 6/17/96
Circuit Description
The Torque Converter Clutch Solenoid Valve (TCC Sol Valve) acts on the
hydraulic fluid, controlling TCC apply and release.
The TCC used is the Electronically Controlled Converter Clutch (ECCC).
The ECCC allows the TCC to slip without excessive wear. This allows smooth
application and release of the TCC. The PCM will normally allow a small amount
of slip to occur with the ECCC. This limits the fluid pressure in the torque
converter. Very high pressure in the torque converter will damage the converter.
When the TCC PWM Sol. Valve engages the TCC, TCC slip speed is approximately
20 RPM.
If the PCM detects 3 occurrences of TCC slip of -20 to +25 RPM
when the TCC is commanded OFF, then DTC P0742 sets. DTC P0742 is a type B
DTC.
Conditions for Setting the DTC
| • | No TP DTCs P0122 or P0123. |
| • | No VSS DTCs P0502 or P0503. |
| • | No TCC PWM solenoid electrical DTC P1860. |
| • | No TCC enable solenoid electrical DTC P0740. |
| • | The engine has been running for 8 seconds. |
| • | The engine speed is 800-4000 RPM. |
| • | The PCM has commanded the TCC OFF. |
| • | The commanded gear is not 1st. |
| • | No gear range change for greater than 3 seconds. |
| • | The transmission gear range is D4, D3, or D2. |
| • | The throttle angle is 14-50%. |
| • | The engine torque is 95-270 N·m (70-200 ft lbs.). |
| • | The vehicle speed is 32-112 km/h (20-70 mph). |
| • | The TCC slip speed is -20 to +25 RPM, 3 occurrences
for 8 seconds. |
Action Taken When the DTC Sets
The PCM illuminates the Malfunction Indicator Lamp (MIL) after two consecutive
trips with a failure reported.
Conditions for Clearing the DTC
| • | The PCM turns OFF the MIL after three consecutive ignition cycles
without a failure reported. |
| • | A scan tool can clear the DTC from the PCM history. The PCM clears
the DTC from the PCM history if the vehicle completes 40 warm-up cycles without
a failure reported. |
Diagnostic Aids
| • | Check for PRNDL DTC P0705. DTC P0705 affects transmission operation.
This may set DTC P0742 falsely. |
| • | Inspect the transmission fluid for debris. |
Test Description
The step number below refers to the step numbers on the diagnostic table.
-
A TCC slip speed of -20 to +25 RPM indicates that this DTC is not current.
Refer to the Diagnostic Aids. Inspect for PRNDL DTC P0705.
DTC P0742 Torque Converter Clutch System Stuck ON (Early Buick)
Step
| Action
| Value(s)
| Yes
| No
|
1
| Was the Powertrain On-Board
Diagnostic (OBD) System Check performed?
| --
|
Go to Step 2
| Go to
Powertrain On Board Diagnostic (OBD) System Check
|
2
|
- Install the Scan Tool
®.
- With the engine OFF, turn the ignition switch to the RUN position.
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze
Frame and Failure Records for reference. Using the Clear Info function will
erase the stored Freeze Frame and Failure Records from the PCM.
- Record the DTC Freeze Frame and Failure Records.
- Select TCC Slip Speed.
Was the TCC slip speed within the range specified?
| -20 RPM to +25 RPM
| Go to Diagnostic Aids
|
Go to Step 3
|
3
| Inspect for the following conditions:
| • | The TCC enable solenoid stuck ON because of sediment. |
| • | The TCC apply valve stuck ON because of sediment. |
| • | Refer to Control Valve Body Assembly Inspection, in this Section. |
Did you find and correct a problem?
| --
|
Go to Step 4
| --
|
4
| In order to verify your repair,
perform the following procedure:
- Select DTC.
- Select Clear Info.
- Operate the vehicle under the following conditions:
| • | The gear range is D2, D3, or D4. |
| • | No gear range change for greater than 3 seconds. |
| • | The commanded gear is not 1st. |
| • | The engine speed is 800-4000 RPM. |
| • | The vehicle speed is 32-112 km/h (20-70 mph). |
| • | The engine torque is 95-70 N·m (70-200 lb ft). |
| • | The throttle position is 14-50%. |
| • | The PCM commands the TCC OFF. |
| • | The TCC slip speed is 150-2000 RPM for 5 seconds. |
- Select Specific DTC. Enter DTC P0742.
Has the test run and passed?
| --
| System
OK
|
Begin the diagnosis again. Go to Step 1
|
DTC P0742 TCC System Stuck On All Other Applications
Circuit Description
The Torque Converter Clutch Solenoid Valve (TCC Sol Valve) acts on the
hydraulic fluid, controlling TCC apply and release.
The TCC used is the Electronically Controlled Converter Clutch (ECCC).
The ECCC allows the TCC to slip without excessive wear. This allows smooth
application and release of the TCC. The PCM will normally allow a small amount
of slip to occur with the ECCC. This limits the fluid pressure in the torque
converter. Very high pressure in the torque converter will damage the converter.
When the TCC PWM Sol. Valve engages the TCC, TCC slip speed is approximately
20 RPM.
If the PCM detects 3 occurrences of TCC slip within -20 to +50 RPM
when the TCC is commanded OFF, then DTC P0742 sets. DTC P0742 is a type B
DTC.
Conditions for Setting the DTC
| • | No TP DTCs P0122 or P0123. |
| • | No VSS DTCs P0502 or P0503. |
| • | No TCC PWM solenoid electrical DTC P1860. |
| • | No TCC enable solenoid electrical DTC P0740. |
| • | The engine has been running for 5 seconds. |
| • | The engine speed is 800-4000 RPM. |
| • | The PCM has commanded the TCC OFF. |
| • | The commanded gear is not 1st. |
| • | No gear range change for greater than 3 seconds. |
| • | The transmission gear range is D4, D3, or D2. |
| • | The throttle angle is 14-50%. |
| • | The engine torque is 95-270 N·m (70-200 ft lbs.). |
| • | The vehicle speed is 32-112 km/h (20-70 mph). |
| • | The TCC slip speed is -20 to +50 RPM, 3 occurrences
for 5 seconds. |
Action Taken When the DTC Sets
The PCM illuminates the Malfunction Indicator Lamp (MIL) after two consecutive
trips with a failure reported.
Conditions for Clearing the DTC
| • | The PCM turns OFF the MIL after three consecutive ignition cycles
without a failure reported. |
| • | A scan tool can clear the DTC from the PCM history. The PCM clears
the DTC from the PCM history if the vehicle completes 40 warm-up cycles without
a failure reported. |
Diagnostic Aids
| • | Check for PRNDL DTC P0705. DTC P0705 affects transmission operation.
This may set DTC P0742 falsely. |
| • | Inspect the transmission fluid for debris. |
Test Description
The step number below refers to the step numbers on the diagnostic table.
-
A TCC slip speed of -20 to +50 RPM indicates that this DTC is not current.
Refer to the Diagnostic Aids. Inspect for PRNDL DTC P0705.
DTC P0742 Torque Converter Clutch System Stuck ON
Step
| Action
| Value(s)
| Yes
| No
|
1
| Was the Powertrain On-Board
Diagnostic (OBD) System Check performed?
| --
|
Go to Step 2
| Go to
Powertrain On Board Diagnostic (OBD) System Check
|
2
|
- Install the Scan Tool
®.
- With the engine OFF, turn the ignition switch to the RUN position.
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze
Frame and Failure Records for reference. Using the Clear Info function will
erase the stored Freeze Frame and Failure Records from the PCM.
- Record the DTC Freeze Frame and Failure Records.
- Select TCC Slip Speed.
Was the TCC slip speed within the range specified?
| -20 to +50 RPM
| Go to Diagnostic Aids
|
Go to Step 3
|
3
| Inspect for the following problems:
| • | The TCC enable solenoid stuck ON because of sediment. |
| • | The TCC apply valve stuck ON because of sediment. |
| • | Refer to Control Valve Body Assembly Inspection, in this Section. |
Did you find and correct a problem?
| --
|
Go to Step 4
| --
|
4
| In order to verify your repair,
perform the following procedure:
- Select DTC.
- Select Clear Info.
- Operate the vehicle under the following conditions:
| • | The gear range is D2, D3, or D4. |
| • | No gear range change for greater than 3 seconds. |
| • | The commanded gear is not 1st. |
| • | The engine speed is 800-4000 RPM. |
| • | The vehicle speed is 32-112 km/h (20-70 mph). |
| • | The engine torque is 95-70 N·m (70-200 lb ft). |
| • | The throttle position is 14-50%. |
| • | The PCM commands the TCC OFF. |
| • | The TCC slip speed is 150-2000 RPM for 5 seconds. |
- Select Specific DTC. Enter DTC P0742.
Has the test run and passed?
| --
| System
OK
|
Begin the diagnosis again. Go to Step 1
|
